| Cell wall polysaccharide is one of the main sources of Lycium barbarum polysaccharide.The study on its metabolism during fruit growth and development can provide theoretical reference for the study of Lycium barbarum polysaccharide metabolism.At present,the metabolic regularity of Lycium barbarum fruit cell wall polysaccharides based on proteomics in the process of growth and development has seldom been reported.Therefore,this study explored the metabolic regularity of cell wall polysaccharides from Lycium barbarum fruit by chemical determination,structural analysis,cell wall metabolic enzyme activity analysis and differential proteomics.Specific research contents are as follows:(1)Taking the "Ning qi No.1" Lycium barbarum fruit as the research object,the composition and structure characteristics of the cell wall in different growth stages were investigated by chemical measurement,Raman spectroscopy,ultrastructural observation and atomic force microscopy.The results showed that the fruit firmness reached the highest at 21 days of growth and then decreased sharply with the fruit maturing,and reached the softest at 35 days.The content of cell wall substances also increased first and then decreased.The content of water-soluble pectin increased sharply after 21 days of fruit growth.Sodium carbonate soluble pectin also increased slightly,while the content of three hemicellulose increased from 7 to 14 days and then decreased.There were pectin peaks at 870 cm-1 in Lycium barbarum fruits at different developmental stages.The characteristic peaks were not obvious in 7-28 days,but appeared in 35 days.Characteristic peaks of cellulose and liemicellulose appeared at 960 cm-1 and 1447 cm-1.The peak intensity reached its maximum on 21 days and then decreased.However,at 35 days,the characteristic peaks overlapped due to the sharp increase of carotenoid interference.Ultrastructural changes of cell wall of Lycium barbarum fruit mainly occurred in 28-35 days,and the cell wall structure gradually collapsed.The water-soluble pectin and sodium carbonate soluble pectin partially depolymerized.(2)During the development of Lycium barbarum fruit,the activity of pectin methylesterase decreased first and then increased,which was related to its frequent growth activities in the early stage of fruit growth,and mainly participated in cell wall depolymerization in the later stage.Polygalacturonase activity showed an overall trend of increase,starting at 14 days and peaking at 28 days.The P-galactosidase activity also showed an increasing trend,which was the highest at 35 days.Cellulase activity was on the rise and reached its maximum at 28 days.The ?-hexosaminidase activity was highest at 21 days and decreased at the later stage of development,but its activity was generally higher during development.Polygalacturonase,?-galactosidase,cellulase may be the main related enzymes in the late depolymerization of the cell wall.In addition,the other two enzymes also play an important role in the modification and metabolism of fruit cell wall polysaccharides.(3)Using iTRAQ technology,the 7 days growth period was used as the comparison group,and the differential protein identification was carried out on the fruit of the 14 days,21 days,28 days and 35 days development periods,and a total of 1799 proteins were obtained.A total of 26 functional proteins related to cell wall activity were screened by GO function annotation.Through the relationship between KEGG pathway enrichment and differential protein expression analysis and cell wall changes and enzyme activity differences,the metabolic mechanism of wall polysaccharides was obtained.The results showed that energy metabolism may be involved in the synthesis and degradation of cell wall polysaccharides.In the early stage of fruit development,the sucrose degradation of the reserve provides energy to promote the De-esterification of pectin,which may be closely related to the cell wall material reorganization of fruit cell volume,and the energy metabolism in the later stage of development exacerbates the demand of D-Glu and UDP-Glu.Increase.Promotes the degradation of cellulose while causing partial degradation and conversion of pectin.The enhanced synthesis of raffinose is an increase in the demand for galactoside,leading to degradation of galactan.After cluster analysis of 1799 differential proteins by K-means clustering method,38 expression pattern categories were obtained,and the proteins under clustering of expression patterns 7 and 32 were selected as candidate differential proteins.Six proteins were screened,including arabinogalactan protein,?-hexosaminidase,hexosyltransferase and P-galactosidase.The verification of the iTRAQ results by the PRM method shows that the results are credible and can be further analyzed. |
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